The present invention relates to a sensor device.
Sensor devices of this kind are used, for example, in electric motors to sense a variety of variables which depend on the rotary motion of the motor armature shaft, for example rotation speed, rotation direction, or rotation angle, and are known, for example, from German Pat. No. 195 25 292. A permanent magnet is arranged on a circuit board in the electronics compartment of the electric motor. The two poles of the magnet are connected to magnetic flux conductors which are guided to the motor armature shaft arranged remotely from the electronics compartment, where an end segment of the magnetic flux conductors is spaced away, by a narrow air gap, from a magnetic flux converter which moves along with the motor armature shaft. The moving magnetic flux converter comprises ferromagnetic and diamagnetic segments which are arranged on a rotary element. Rotation of the motor armature shaft results in rotation of the magnetic flux converter, thus causing a change in the magnetic flux in the magnetic circuit constituted by the permanent magnet, the magnetic flux conductors, and the magnetic flux converter. A Hall sensor arranged on the circuit board above the permanent magnet senses the magnetic field change of the leakage field as it changes, and as a function of the change generates an electrical output signal which is delivered to a motor control circuit connected to the Hall sensor.
Also known are sensor devices, for use in an electric motor, in which the magnetic flux converter which moves along with the motor shaft comprises a permanent magnet, nonrotatably joined to the motor armature shaft and configured as an annular magnet, which at the same time is the magnetic field source. Stationary magnetic flux conductors face the annular magnet with their ends which are provided as pickoffs. Associated with the other end of the magnetic flux conductors, facing away from the motor armature shaft with the magnetic flux converter, is a Hall IC which is arranged as a surface-mounted device (SMD), for example on a circuit board in an electronics compartment of the electric motor. Here again, rotation of the motor armature shaft results in a change in the magnetic flux induced in the magnetic flux conductor, and thus in a change in the magnetic field signal sensed by the Hall IC. The Hall IC converts the signal into a digital electrical signal which is analyzed by the motor control electronics arranged on the circuit board and is used to control the motor.
The sensor device according to the present invention has, in contrast thereto, the advantage that the space required for accommodating the Hall sensors and the electronic control circuit on the support element provided therefor, which for example can be a circuit board, can be considerably reduced. For example, circuit elements belonging to the control electronics, for example the program memory, microprocessor, or EPROM, can be combined with the Hall IC component into an application-specific integrated circuit (ASIC) which is placed onto the circuit board as an individual component. The outlay for component placement on the circuit board is thereby considerably reduced, so that overall costs can be decreased. Cost decreases also result from the fact that the manufacture of an individual ASIC component is considerably more economical than the manufacture of a circuit board onto which all the components necessary for the electronic circuit are placed individually. Advantageously, the magnetic signals are transferred by the magnetic flux conductors directly to the Hall sensor element of the application-specific integrated circuit. The ASIC component can thus be arranged remotely from mechanically moving parts, for example the motor armature shaft of an electric motor, in a manner protected from dirt and moisture. In addition, the small ASIC component can be protected from dirt and moisture more easily than can a complex electronic circuit arranged on a circuit board, thereby also enhancing the overall reliability.
For example, it is advantageous to arrange the ASIC component on a support element, remotely from the magnetic field converter, between the ends of two magnetic flux conductors, so that the magnetic field is optimally sensed by the Hall sensor element contained in the ASIC component.
Magnetic field detection by the Hall sensor element of the ASIC component can be further improved by the fact that a projection of one magnetic conductor passes through an opening in the support element to the mounting surface of the ASIC component.
It is particularly advantageous that if the magnetic flux conductors are in thermally conductive contact with the ASIC component, the magnetic flux conductors can serve not only as signal conductors but also as a heat sinks to dissipate the heat generated by the ASIC component.